Xilinx FPGAs guide robotic-assisted surgical system

Editor’s Note:This article is reproduced from the Fall 2011 Edition of Xcell Journal, with the kind permission of the editor, Make Santarini.

Saving lives, reducing recovery times – it’s all about the patient. This is the proud mantra of one of the most interesting companies in the medical-device industry: Intuitive Surgical.

Already in use at more than 1,500 sites worldwide and proven in hundreds of thousands of patient surgeries, the company’s robotic-assisted da Vinci Surgical Systems are the state of the art in minimally invasive surgery (MIS), allowing patients to recover much sooner than they would from traditional open surgical procedures.

Intuitive Surgical has used Xilinx FPGAs since 2003, leveraging new device families over successive years to create ever more sophisticated versions of the da Vinci and to expand its use. Surgeons now employ the tool in a range of urologic, gynecologic, cardiac, thoracic, head and neck, as well as general surgical procedures.

The da Vinci Systems consist of three main interconnected components: a surgeon console, patient-side cart and vision system (Figure 1). The surgeon console is essentially a cockpit for surgeons doing a given procedure. Rather than standing over a patient and bending for hours to perform an operation – as is the case with traditional surgeries – physicians using the da Vinci System sit comfortably at the console with their fingers on the master controllers (Figure 2) and their eyes positioned in a 3D viewer. Here, they can see the target anatomy magnified to their liking and view the surgical instruments they’ll use for the procedure.

Figure 1. The da Vinci System improves surgical outcomes and speeds patient recovery. In this picture, physicians sit at dual surgeon consoles, at the left and left middle. The vision system is pictured in the right middle, while the patient-side cart is at the right.

The da Vinci System translates the movements of the surgeon’s fingers and wrists in real time to guide robotic arms on the patient-side cart accordingly. Surgeons manipulate the controllers to guide various surgical instruments – scalpels, clamps, scopes, cauterizing and suturing needles, and so on – which are positioned at the end of individual robotic arms on the patient-side cart. From the comfortable cockpit, surgeons perform every critical step of the surgery, from initial cut to the final suturing, while OR assistants monitor the patient.For its part, the third instrument connected to the da Vinci System, the vision system, is equipped with a high-definition, 3D endoscope (a tube with a camera and light at the tip) and image-processing equipment that provides true-to-life images of the patient’s anatomy. The vision system also gives the entire OR team and surgical assistants at the patient’s side a wide-screen view of the operating field.

Figure 2. The surgeons position their hands in the specialized instruments (bottom picture). The da Vinci System computes their subsequent movements in real time and guides robotic arms (seen in close-up at top) on the patient-side cart, which is positioned over the area of the patient where the surgery will be performed.

For medical facilities, da Vinci provides great advantages over traditional surgical procedures in that it allows surgeons to perform complex operations using a minimally invasive approach, more comfortably and with less fatigue. What’s more, the system minimizes hand tremors, enhancing the precision of surgeons’ movements and thus, potentially, extending their careers.

Chris Simmonds, senior director for marketing services at Intuitive Surgical, said doctors benefit from the enhanced visualization and system ergonomics, reporting less eye strain and improved dexterity and control, especially for procedures that require very high magnification. “One doctor shared that he can now do seven or eight reverse-vasectomy procedures per day, instead of the two-per-day rate prior to da Vinci,” said Simmonds.

But the biggest advantages of the system, said Sal Brogna, senior vice president of engineering at Intuitive Surgical, are for patients. “Patients are first and foremost in our minds at Intuitive Surgical, and helping patients have better surgical outcomes and faster recovery is what drives our company and the engineering decisions behind our technology,” he said. “The da Vinci allows surgeons to be more precise. More-precise procedures mean shorter recovery times – and less time in the hospital makes all patients and their families happier.”

Originally inspired by technology advances stemming from research at the Defense Advanced Research Projects Agency (DARPA), Intuitive Surgical’s robotic MIS system presented numerous engineering challenges for its developers. One area, video processing, has become increasingly important as the da Vinci models have evolved from 3D standard-definition stereo vision to today’s dual-console, multiwindow 3D high-definition (HD) system.

“When we were updating the original video-processing subsystem, we wanted to introduce multi-windowed video sources for the surgeon, so they could monitor vital patient data during surgeries,” said David Powell, principal design engineer for Intuitive Surgical’s video-processing solutions. “An increase in video-processing bandwidth would allow us to display data from auxiliary video sources, along with the view of the operating field. For example, surgeons would have instant feedback from an ultrasound or heart-lung machine without taking their eyes off of the procedure in progress.”

Brogna said that in addition to the technical challenges involved in giving surgeons an expanded, immersive view that could shorten procedures and improve outcomes, the video solution also had to comply with stringent safety and reliability requirements. This meant that the system needed to be flexible, upgradable and, of course, reliable.

All these requirements led Intuitive Surgical to ultimately employ a Xilinx Virtex FPGA in the video-processing design for its second-generation da Vinci Surgery Systems, which it designed in 2003. “We initially selected a Xilinx Virtex-2 Pro FPGA solely on the performance of the DSP elements for streaming video,” said Powell. “The embedded processor Xilinx had available for that device was a ‘nice-to-have’ feature. We realized we could take advantage of it to reduce the real estate for video processing, but the embedded processor wasn’t a fundamental reason for our selection of the Xilinx device.”

As it turned out, however, “Xilinx’s embedded-processor architecture has led to a pretty major revolution for us in terms of our subsequent platform designs throughout the entire system,” Powell said.

FPGAs help usher in modular designs Intuitive Surgical’s first experience with Xilinx devices led the company to follow the FPGA technology curve and add more-advanced system functionality to the latest Xilinx FPGAs as they became available. “As we started using the Xilinx device, we discovered it to be quite a nice design platform – so nice, in fact, that follow-on platforms have evolved to employ dozens of Xilinx FPGAs in all of the main system components,” said Powell. “Today, we can fit so much in each FPGA [that] we can turn a board into a chip, pretty much.”

Although Intuitive’s engineers did not leverage embedded processors in the FPGA designs they employed in the early generations of the da Vinci System, they did in the last two generations. For example, Intuitive used the Virtex-5 FX FPGA’s PowerPC hard processor and MicroBlaze soft processor in many modules in the last two generations of da Vinci Systems. Powell said that FPGA block/design reuse has also been a key in helping Intuitive Surgical bring new generations of its system to market sooner.

“Using a cookie-cutter approach, we have been able to standardize many functions and build these blocks into new designs very quickly,” said Powell. “Our first board to employ a Xilinx FPGA was up and running in two hours. After that, we found we could get a board up and running in just minutes – these kinds of results are almost unheard of.”

By reusing cores in successive generations of the system and adding system functionality to new generations of FPGAs, the company has been able to move to a more distributed architecture for da Vinci and usher in the module era, in which customers can add several modules to a single system to suit their particular needs. For example, Brogna said that the distributed architecture helped the company introduce systems with dual consoles. “Now two surgeons can collaborate in a robotic MIS procedure, or set up a trainer-student configuration,” said Brogna. “The modular designs, which leverage Xilinx FPGAs, contribute to this capability and mark a major milestone in our product line.”

Brogna said that prior to using Xilinx FPGAs, da Vinci component interconnections were varied and complex. The modules were linked via four large “garden hose” size cables, which wore out too quickly due to constant manipulation during surgical setup in the operating rooms. More significantly, system components had to be manufactured – and repaired – as an integrated unit. Thus, if one component needed repair, the entire system was out of action. Today, a single-fiber cable design provides standardized connections among all system components. The Xilinx hard-processor blocks and high-speed DSP slices provide system-on-a-chip capabilities that support eight channels of full 1080i HD video (20 Gbps) across the simplified interconnect. This new interconnect technology has cut failure rates dramatically.

Brogna said that Intuitive Surgical’s modular design has also revolutionized manufacturability, testability, reliability and serviceability. “A flexible, customizable design block made us think about everything in new ways – we now focus on modules and cards,” said Brogna. “Even manufacturing doesn’t talk about shipping systems – they talk about cards. This has made us incredibly agile and effective in terms of producing and testing products and servicing systems in the field.”

The power of programmability also means simplified updates. Brogna said that instead of replacing modules or subsystems, Intuitive Surgical can introduce new functionality or enhance existing functionality with an in-field firmware upgrade. Service teams can also quickly query for consistency across all the processors in the system, for improved process control and to ensure that systems are optimally configured for surgery.

Powell pointed to a close partnership with Xilinx’s technical staff, sales force and executives as another key to success. “We know Xilinx devices backwards and forwards now, and this really helps us make a difference in many lives,” he said. “It always comes back to the patients. We hear from people every day who tell us how a new procedure changed or saved their life. That’s what motivates us to deliver the best technology.”

About the authorMike Santarini is the publisher of Xilinx’s Xcell Journal magazine. Mike can be contacted via email at mike.santarini@xilinx.com

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